1. Field of the Invention
The present invention generally relates to a structure of a magnetic head used to record/reproduce a signal on/from a magnetic tape in a magnetic recording and/or reproducing apparatus known as an audio signal recording and/or reproducing apparatus with employment of a magnetic tape. More specifically, the present invention is directed to improvements in a head structure of a magnetic head used while being fixed on a portion of a magnetic tape transporting path, and also a magnetic recording and/or reproducing apparatus with using this magnetic head.
2. Description of the Prior Art
In the conventional magnetic recording and/or reproducing apparatus (for instance, audio signal recording and/or reproducing apparatus) using the magnetic tape 51 as shown in FIG. 1, the signal is recorded on the magnetic tape 51, or the signal is reproduced from the magnetic tape 51 by sliding this magnetic tape 51 and the fixed magnetic head 52. This magnetic head 52 is fixed on a portion of the transporting path of the magnetic tape 51.
Such a fixed magnetic head 52 contains the recording and/or reproducing portion 53 which is slid on the magnetic tape 51. This recording and/or reproducing unit 53 constitutes the housing of the fixed magnetic head 52. This recording and/or reproducing unit 53 is filled into the shield case 54 by using resin 55 in such a manner that this recording and/or reproducing portion 53 is outwardly exposed through the window portion formed in a predetermined position of the shield case 54 made of, for example, a magnetic material such as an Fe--Ni alloy.
Since the sliding characteristic of the resin 55 with respect to the magnetic tape 51 is deteriorated, the exposed area of this fixed magnetic head 52 with respect to the sliding surface of the magnetic tape is preferably minimized. To avoid magnetic coupling between the shield case 54 made of the magnetic material and the magnetic core 56 similarity made of a magnetic material, which magnetic core constitutes the recording and/or reproducing portion 53, the magnetic core 56 must be sufficiently separated from the shield case 54.
As a result, in order to reduce the exposed area of the resin 55, the following method has been introduced. That is, the sliders 57 and 69 made of non-magnetic materials are provided with the recording and/or reproducing portion 53 in addition to the magnetic core 56. In other words, as illustrated in FIG. 3 and FIG. 4, this recording and/or reproducing unit 53 is constituted by setting the sliders 57 and 69 on both sides of a single magnetic core 56. As a concrete non-magnetic material used in such sliders 57 and 69, a metal alloy made of a non-magnetic material, and a sintered body are employed.
On the other hand, as represented in FIG. 2, there is such a magnetic recording and/or reproducing apparatus by employing the rotary head 60 independent from the above-explained magnetic recording and/or reproducing apparatus constituted only by the fixed magnetic head 52. Similar to a video signal recording and/or reproducing apparatus used in a VTR, in order to record/reproduce signals in a frequency range over several MHz, video signals are recorded and/or reproduced on/from the magnetic tape 58 by the rotary magnetic head 60 formed on the rotary drum 59 by the helical scanning system. The rotary magnetic head 60 is arranged in such a manner that this rotary magnetic head 60 is inclined with respect to the transport direction of the magnetic tape 58.
Also, in such a magnetic recording and/or reproducing apparatus, the control signals, the audio signal, or the data signals other than the signals recorded and/or reproduced by the rotary magnetic head 60 are recorded and/or reproduced, depending upon use purposes, by the fixed magnetic head 61 for the control signal, and the fixed magnetic head 62 for the audio signal, which are fixed on positions different from the rotary drum 59.
However, the above-described conventional magnetic recording and/or reproducing apparatuses shown in FIG. 1 and FIG. 2 have the below-mentioned problems to be solved.
First, in the magnetic recording and/or reproducing apparatus indicated in FIG. 2, as the recording and/or reproducing portion 53, the composite structure constructed of the magnetic core 56 made of the magnetic material, and also the sliders 57 and 69 made of the non-magnetic material. Considering now abrasion (wearing) characteristic of such an recording and/or reproducing portion 53 with respect to the magnetic tape 51, it is preferable to realize that the abrasion characteristic of the magnetic core 56 is made coincident with that of the sliders 57 and 69. However, conventionally, it is particularly difficult to select the non-magnetic material of the sliders 57 and 69, which has the abrasion characteristic equivalent to that of the magnetic material of the magnetic core 56.
Assuming now that the sliders 57 and 69 are made by employing such a non-magnetic material having an abrasion characteristic relatively lower than that of the magnetic material of the magnetic core 56, as represented in FIG. 3, the magnetic core 56 is abraded faster than the sliders 57 and 69, so that the surface of the magnetic core 56 is brought into a concave condition with respect to the sliders 57 and 69. As a result, this concave condition may impede better contacts established between the magnetic tape 51 and the magnetic core 56, and further the recording and/or reproducing operation of the magnetic tape 51 by the recording and/or reproducing portion 53 cannot be smoothly carried out.
On the other hand, assuming now that the slider 57 and 69 are made by employing such a non-magnetic material having an abrasion characteristic relatively higher than that of the magnetic material of the magnetic core 56, as represented in FIG. 4, sliders 57 and 69 are abraded faster than the magnetic core 56, so that the surface of the magnetic core 56 is brought into a convex condition with respect to the sliders 57 and 69. As a result, this convex condition may increase pressure at the contact surface of the magnetic tape 51 with respect to the magnetic core 56. As a result, abrasion of the magnetic core 56 is increased, so that the lifetime of the fixed magnetic head 52 would be considerably shortened.
Under such circumstances, conventionally, an Fe--Al--Si alloy and/or Co series amorphous are employed to manufacture the magnetic core 56, whereas such a non-magnetic material as a Cu series alloy, e.g., nickel silver is employed to manufacture the sliders 57 and 69, which owns an abrasion characteristic slightly higher than that of the magnetic core 56.
However, although the sliders 57 and 69 made of the abrasion characteristic slightly higher than that of the magnetic core 56 can maintain the better sliding condition between the magnetic core 56 and the magnetic tape 51, the abrasion of the magnetic core 56 is similarly increased. Therefore, this matrical cannot prevent the lifetime of the fixed magnetic head 52 from being shortened.
On the other hand, as illustrated in FIG. 5, in the magnetic recording and/or reproducing apparatus shown in FIG. 2, since the video signal is recorded by the rotary magnetic head 60 in such a manner that this video signal occupies a major portion of a center portion of the magnetic tape 52 along the width direction (namely, upper/lower direction) (video track), the control signal, the audio signal, or the data signal may be recorded on the edge portions of this magnetic tape 58 by the fixed magnetic heads 61 and 62 along the width direction (control signal track, audio track etc.).
However, in such a magnetic recording and/or reproducing apparatus, as illustrated in FIG. 2, pressure at the contact surfaces of the magnetic tape 58 with respect to the fixed magnetic heads 61 and 62 is made unequal to each other along the width direction of the magnetic tape 58. In other words, as shown in FIG. 6, as to the fixed magnetic head 62 indicated in FIG. 5, pressure at the contact surface of the magnetic tape 58 on the edge side 58a (upper edge portion shown in this drawing) along the width direction is higher than that of the magnetic tape 58 on the center portion side (lower portion shown in this drawing) along the width direction.
As a result, the abrasion of the slider 66 positioned opposite to the edge portion 58a of the magnetic tape 58 along the width direction is considerably increased, as compared with the abrasion of the magnetic core 65, and also the abrasion of the slider 67 arranged on the center portion side of the magnetic tape 58 along the width direction from this magnetic core 65. As a consequence, there is such a problem that this may impede the sliding operation established between the magnetic core 65 and the magnet tape 58.
On the other hand, similar to the above-described fixed magnetic head 52, in FIG. 6, the recording and/or reproducing portion 63 constituted by the magnetic core 65, and the sliders 66, 67 is filled into the shield case 64 for forming the housing of the fixed magnetic head 65 by using resin 68.
To solve these problems, the applicant of the present invention has proposed "MAGNETIC HEAD STRUCTURE" disclosed in Japanese Unexamined Patent Application No. 8-20227 opened in 1996. This magnetic head structure is featured by that, as shown in FIG. 7, the material having the abrasion characteristic higher than that of the magnetic core 15 is employed to fabricate the slider 16 positioned opposite to the edge portion (upper edge portion shown in the drawing) 14a of the magnetic tape 14 along the width direction, over which this edge portion 14a of the magnetic tape 14 along the width direction thereof is slid, and where pressure at the contact surfaces of the magnetic tape 14 is increased.
Then, similar to the conventional magnetic head, the abrasion characteristic of the slider 17, which is slightly higher than that of the magnetic core 15, on the center portion side of the magnetic tape 14 along the width direction is employed to manufacture this slider 17. Accordingly, in the case that the magnetic tape 14 is slid over the magnetic core 15 and the sliders 16 and 17, the following conditions occur.
That is to say, similar to the conventional magnetic head, the abrasion of the slider 17 is slightly increased, as compared with that of the magnetic core 15, so that the surface of this slider 17 is brought into the concave condition with respect to the magnetic core 15. Since the slider 16 employs such a material having the abrasion characteristic lower than that of the magnetic core 15, even when the contact surface pressure of the edge portion 14a of the magnetic tape 14 along the width direction is high, this slider 16 is not considerably abraded different from such a slider 66 of the conventional fixed magnetic head shown in FIG. 6. Thus, the abrasion amount of the slider 16 becomes equal to that of the magnetic core 15, so that the better sliding operations between the fixed magnetic head and the magnetic tape 14 can be maintained for a long time duration.
However, in the VTR with employment of such a video signal recording and/or reproducing apparatus indicated in FIG. 2, since various formats are introduced and the tape tension applied to the magnetic tape is different from each other with respect to each of these different formats, the contact surface pressure of the edge portion of the magnetic tape along the width direction with respect to the fixed magnetic head is different from each other, depending upon variations in this tape tension. Also, since many sorts of magnetic tapes are employed, the degrees of the polishing characteristics of these magnetic tapes which may abrade the above-explained slider are different from each other.
As a result, even such a conventional fixed magnetic head shown in FIG. 7 may have the following negative possibility, depending upon a certain combination between the tape tension and the sort of magnetic tape by the above-explained format. That is, as represented in FIG. 8, both the abrasion amount of the slider 16 slid over the edge portion 14a of the magnetic tape 14 along the width direction becomes smaller than the expected abrasion amount, and thus, the surface of the slider 16 is brought into the convex condition with respect to the magnetic core 15, which may impede the better sliding operation between the magnetic core 15 and the magnetic tape 14.